By Kaitlyn Franz, Test and Measurement Product Manager
USB instruments are a commonly featured topic in Test and Measurement media. With new devices constantly launching, an especially heated debate is standalone oscilloscopes vs USB oscilloscopes. With the debate, comes misconceptions. Here’s the bottom line, there are going to be cases where one fits the application better than the other. However, the portable versions mature, they are starting to become more useful and more advanced. For example, the Analog Discovery 2 has an oscilloscope, spectrum analyzer, logic analyzer, and 9 other tools, and like many USB instruments, is good enough for most things.
In order to attempt to combat misinformation, I have listed some common misconceptions about USB oscilloscopes.
1. They require extra hardware and use more bench space than a standalone scope
This one is true assuming you don’t have a laptop anyway. With a USB Oscilloscope you need a computer to run the software. However, most people carry around laptops anyhow. I have a tiny computer that I bought on amazon for $200 that I use when I’m traveling. So the required hardware includes; your computer, and a device that fits in a pocket.
It’s hard to imagine carrying around a benchtop oscilloscope anyways.
It’s important to note that this combination can do much more than a single instrument Oscilloscope. Since, the software does most of the signal processing and manipulation, some USB oscilloscopes also feature other instruments like impedance analyzers, logic analyzers, and more. Additionally, unlike a benchtop scope, this combination of hardware, can be used to analyze circuits, provide a platform to view and record data, play music or podcasts, browse the internet, and chat with friends or coworkers. Point being, you probably already have your laptop near you, and so a little extra hardware is worth it when it provides many more functions other than just operating that USB scope.
For example Analog Discovery 2 includes an oscilloscope, waveform generator, power supplies, voltmeter, data logger, logic analyzer, digital pattern generator, virtual I/O, spectrum analyzer, network analyzer, impedance analyzer, and protocol analyzer.
2. The GUI will be difficult to use
The user interface on most USB scopes is a piece of software that is installed on a computer. If the expectation is that this act like a benchtop scope, then it might have a slight learning curve. However, well designed software, such as WaveForms is designed to balance the look of a benchtop oscilloscope, with familiar features that are common among all computer applications. So, if you use other computer applications regularly, the interface should be relatively intuitive to navigate.
Unique to USB oscilloscopes, is in-application documentation. If you can’t figure out how to do something, or wonder if a feature exists, the user guides are often built in to the software and searchable. For example, WaveForms has the help tab, which is open automatically. If you get stuck, switch to the help tab and you can find what you need.
An additional feature that is unique to USB or PC oscilloscopes, is that most of the heavy lifting of the instruments is implemented in the software. This allows the developers to constantly improve the functionality and performance of the device and add new features. For example, updates to WaveForms have included a protocol analyzer instrument and an impedance analyzer instrument. These were both huge value adds at no additional cost to the end user.
3. They only provide fixed step ranges
This is false. Sometimes this appears to be the case if only fixed step values appear, but most interfaces also include type in values. In WaveForms the scroll wheel can fine tune the values just like a knob on a traditional scope.
4. They have a very limited range, some only 5V!
This depends but is not generally true. The Analog Discovery 2 has an input range of ±25V. Other USB Oscilloscopes have a large variety of input ranges, both above and below ±25V.
5. The cost of the scope + Laptop is more than a standalone scope
Assuming you already have a computer, then you’ll only have the cost of the USB Oscilloscope, which usually ranges between $100 – $400. Let’s presume you don’t. Say you buy an Analog Discovery 2 for $279. I can find a laptop with an Intel core i7 with a 1TB hard drive and additional solid state drive for around $1000, this is way overkill for running WaveForms, but maybe you want to run other applications. The cost is still less than many benchtop Oscilloscopes. Assuming I buy a $200 laptop to run WaveForms, the cost is less than $500.
6. They communicate over USB so they are slow and sluggish
Data acquisition happens on the USB scope itself, then once a set limit has been reached, data is sent over USB to the software. For example, the Analog Discovery 2 performs acquisition up to 100MS/s of up to 16k samples, then takes 6ms to read to the PC. The device can also continuously stream up to 1MS/s. So, there are limitations, but certainly not slow and sluggish.
I have both a standalone scope and a the Analog Discovery 2. Clearly, each one has its limitations and strengths, but don’t let misconceptions allow you to make the wrong choice.
Personally, I’d rather have the USB Oscilloscope in my back pocket.
The examples in this article used the Analog Discovery 2.
Sponsored content by Digilent, Inc.